The invention relates to a dosing mechanism for an injection device, by means of which a preferably liquid product, in particular a medicament, can be administered or discharged. In particular, the invention also relates to an injection device comprising such a dosing mechanism. By means of the dosing mechanism, a dose to be administered can be set. The dosing mechanism can be part of a drive mechanism, so that it can preferably also be a dosing and drive mechanism. The mechanism can prevent the setting of a dose, which, for example, exceeds the quantity of a product to be administered in a product container of the injection device.
The term “medicament” here covers any free-flowing medicinal formulation that is suitable for controlled administration through a means such as, for example, a cannula or a hollow needle, comprising, for example, a liquid, a solution, a gel or a fine suspension containing one or more medicinal active substances. A medicament can be a composition with a single active ingredient or a premixed or co-formulated composition with several active ingredients from a single container. Medicaments include drugs such as peptides (for example, insulin, insulin-containing medicaments, GLP-1-containing as well as derived or analogous preparations), proteins and hormones, biologically obtained or biologically active ingredients, active ingredients based on hormones or genes, nutrient formulations, enzymes, and other substances both in solid (suspended) or liquid form, but also polysaccharides, vaccines, DNA or RNA or oligonucleotides, antibodies or parts of antibodies as well as suitable base, auxiliary and carrier substances.
In particular, the invention relates to a dosing mechanism that prevents the setting of a dose to be administered higher than a predetermined value. Thus, the setting of a dose can be prevented even when sufficient quantities for further injections are still present in the product container. As a result, it is advantageously possible to predetermine a desired dischargeable product quantity by means of the device and not by way of the total quantity contained in the product container.
From the prior art, numerous dosing mechanisms are known, which prevent the setting of a dose exceeding the medicament quantity in a reservoir of an injection device.
By means of injection devices known from the prior art, product doses can be set with a dosing mechanism and subsequently discharged from the product container. The case can occur in which a larger dose was set with a dose-setting element than can be discharged from the product container, since the product container contains a smaller product quantity than the dose that had been set. This can lead to the discharge of less product than had been set, which, depending on the discrepancy, can lead to varying degrees of problems for the patient.
For example, in the published, unexamined application WO 2004/078226 A2, a drive mechanism for drug administration apparatuses is described. This drive mechanism contains a housing, a dose-setting sleeve and a two-part piston rod. In an embodiment, a drive sleeve extends downward along an inner portion of the piston rod, when a dose is selected. The distance covered here corresponds to the discharge stroke of the piston needed for the dose. If a subsequent dose is selected, the drive sleeve continues to move along the piston rod. The position of the drive sleeve thus corresponds to the medicament quantity still contained in the cartridge. When the drive sleeve then reaches the end of a thread pitch on the inner portion of the piston rod and as a result cannot rotate further, this corresponds to an empty cartridge.
Another example is described in the published, unexamined application U.S. Pat. No. 6,582,404 B1, which shows a limitation mechanism for drug administration apparatuses, which prevents the setting of a dose that exceeds the residue remaining in the cartridge. The administration device has a dose-setting element, which, when a dose is set by turning relative to a driver, is moved away from a fixed abutment.
The dose-setting element is connected here to the driver in such a manner that it can be turned in a direction without also moving said driver. The dose is administered by turning the dose-setting element back, and the dose-setting element then also moves the driver. The turning driver causes a discharge movement of the piston rod. The driver is connected to a track whose length corresponds to the medicament quantity nominally contained in the cartridge. In this track, a track follower runs, which is connected to the dose-setting element. Each time a dose is selected, the track follower continues to move in the track. When the track follower has reached the end of the track, the dose-setting device cannot be turned further, and a dose-setting higher than the residue still remaining in the cartridge is prevented.
Another example of such an apparatus is described in EP 0 554 996 A1 and shows an injection device for administering liquid such as insulin into body tissues. This injection device contains a dose-setting mechanism, which has a units counter ring and a tens counter ring. A transmission member is provided in order to selectively couple the units counter ring to the tens counter ring, so that they turn together only in selected sections during the dose setting. The dose set is indicated by means of numbers on the rings. Furthermore, the injection device comprises a dose limiting mechanism, which limits the movement of a guide spindle for the provided piston movement in the cartridge, wherein protuberances in the plunger reach the end of grooves along the guide spindle and prevent further movement. The dose limiting mechanism is provided separately from the dose-setting mechanism.
Finally, WO 2006/086983 A1 shows an example of a dose-setting device for self-injection apparatuses with a dose limiting mechanism, which comprises two turning parts, wherein the first part turns continuously during the setting of a dose, and, after a certain rotation position has been reached, the second part in each case also turns in some sections via a selective coupling device. The result is that the second part turns discontinuously over a smaller angle than the first part. The turning of the second part is then limited by an abutment fixed to the housing, which prevents a dose-setting higher than the residue still remaining in the cartridge.
From WO 2010/149209 A1, an injection device is known, which comprises a dose-setting device and coupled to the latter an element, which, during a dose setting, can be rotated relative to another, second element and, which, during a dose discharge, is fixed in rotation relative to the second element. The first element and the second element are connected via a coupling member, which can be spherical, annular, nut-shaped or segment-shaped, for example. Furthermore, a stop abutment is provided, wherein, during a dose setting, the coupling member executes a movement to a stop position, wherein, in the stop position, the coupling element prevents the setting of a dose.
WO 2013/170392 A1 describes a dosing mechanism, which prevents the setting of a dose to be administered above a predetermined value in a reliable and space-saving manner. For this purpose, during the dose setting, a first and a second stop means can run in each case through a path. The paths described by the first and second stop means are self-enclosed and can be run through repeatedly by the first stop means and/or second stop means until, at the stop position, the stop means come in mutual abutment, as a result of which, during the dosing movement, a blocking of the movement of the limiting means relative to one another is achieved.